This invention relates generally to resist processing apparatuses and more particularly to a resist coating apparatus for applying a resist on a semiconductor substrate in a solvent atmosphere.
In semiconductor device manufacturing processes, various kinds of patterning are carried out by using photoresists, electron beam resists, etc. (hereinafter called merely resists or resist) by an exposing, a developing or an etching method. It is required for such a manufacturing process to coat evenly the resist on the substrate, and therefore, various kinds of resist coating apparatus for achieving even coating of the resist have been proposed.
One typical example of conventional apparatus provides a resist coating apparatus in which a liquid state resist is dropped on the central portion of the substrate in the solvent atmosphere. Then the substrate is rotated so that the resist is evenly spread on the entire surface of the substrate by the centrifugal force of the rotating substrate.
With the conventional resist coating apparatus of the described type, however, a vortex or swirly flow of solvent vapor occur in the coating vessel which swirly flow adversely causes vapor pressure difference in the coating vessel, resulting in uneven drying speed of the resist on the substrate. This causes unevenness of the viscosity of the resist and finally unevenness of the thickness of the resist film coated on the surface of the substrate.
The unevenness of the thickness of the coated resist film adversely affects the improvement of the quality and the yield of the substrate because the dimension or size of the pattern formed on the substrate changes in accordance with the thickness of the coated resist film.